ND - Plasticity and Learning - Week 5 Flashcards
List two purposes of the critical period during early development.
Helps to fine tune and calibrate cortical cells - for example with regard to orientation selectivity and disparity cells that code for stereoscopic depth.
Adapt the developing nervous system to the environment.
What two synaptic mechanisms enable experience-dependent plasticity?
Long-term potentiation and long-term depression
Describe what is meant by a Hebbian synaptic mechanism.
When an axon of cell A excites cell B repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells so that cell A’s efficiency as one of the cells firing cell B is increased.
What do synapses with vigorous pre- and post-synaptic activities undergo? What about those with poor or no presynaptic activity?
Vigorous - long-term potentiation
Poor - long-term depression
What underpins ocular dominance shift?
Hebbian synaptic mechanisms
Describe three theories about the termination of the critical period related to axonal changes.
When axonal growth stops
When they lose their ability to change terminal length
Due to changes in the ECM or myelination by glia
Describe two theories about the termination of the critical period related to the synapse.
When synaptic transmission has fully matured
From changes in post-synaptic receptors
Describe a theory about the termination of the critical period related to cortical areas.
When activity of neuromodulators in certain cortical areas decline
List two classical dogmas related to plasticity beyond the critical period and describe the consequence.
Nerve cells in adults dont divide
There is no significant growth of nerve fibres
Only changes in synaptic strength can mediate plasticity (learning, memory, recovery etc)
Can plasticity be restored in adults?
Sometimes
Neural stem cells have been shown to divide, differentiate, and even find the right targets and behave within normal physiological ranges
Axons and dendrites can sprout
Consider a region of the cortex that loses its afferent input. What happens following this loss?
It gets input from the adjacent cortical areas
Describe the stages of response to partial loss of input to the sensory cortex:
Immediate/hours (1)
Hours/days (2)
Weeks/months (2)
Immediate/hours -unmasking of new responsiveness Hours/days -new filtering of the unmasked responsiveness -synaptic filtering Weeks/months -slocal axonal sprouting -dendritic remodelling
What location is perceptual learning specific to? What idea does this lead to (area specifically)?
Specific to the retinal location of the stimulus, leading to the idea that it occurs early along the visual pathway, probably V1
Is perceptual learning influenced by top-down processes?
Yes
